Aerospace Patents 2010

Microfluidic channels in bioanalytical devices are frequently controlled using miniature pneumatic valves; however, these valves do not always provide sufficient precision and reliability. This invention describes an electro-hydraulic valve that gives more control than a comparable pneumatic unit. Created in an elastomeric material, the valve is designed with a flow channel that is crossed by a hydraulic control channel. Two Peltier devices are attached to flexible membranes that separate the control channel from the flow channel. When activated, the Peltier devices apply a hydraulic force against the membranes to deform them, thereby closing or opening the flow channel.

The use of GPS for launch vehicle tracking often requires the use of multiple GPS receivers to ensure a strong and continuous signal. This system provides an economical way to employ several antennas with a single receiver. The antennas are mounted on opposite sides of the launch vehicle. A microwave hybrid combiner receives the antenna signals and generates two outputs representing their sum and difference. These outputs are fed into a single-pole, double-throw switch that toggles between them at a constant or periodic rate. The output of the switch is fed into the GPS receiver. The invention eliminates signal drop-outs and increases signal gain with minimal cost and complexity.

GPS systems for critical applications are often coupled with inertial navigation systems to increase resistance to jamming or interference. When the inertial measurements of a navigation processor are used with a GPS signal tracking and acquisition system, the system is said to be tightly coupled. A refinement of this technique is known as ultratight coupling; in this case, the receiver does not attempt to control code replicas for exact code phase alignment with the incoming signal but merely seeks to observe the deviation of the incoming signal from locally generated replicas and feed that information back to the code replica generators. One problem with ultratight receivers is that they do not lock onto the incoming signal, so lock detectors cannot be used for signal validation. This invention describes a method for validating signals in ultratight receivers. It employs an observation lock detector that receives quadrature (I and Q) correlations from a correlator as well as residual estimates from a prefilter and noise estimates from a noise estimator. This information is transformed into correlation outputs that are then communicated to a conventional lock detector to validate the signal being fed to the Kalman filter. The process improves GPS receiver performance in low signal-to-noise environments; in addition, any errors detected can be used as a measure of performance.

Conventional ion propulsion thrusters have a very large specific impulse but require thousands of volts and very high power. Liquid metal field-effect electrostatic propulsion thrusters (FEEP) greatly reduce the voltage while still having a large specific impulse. Micromachining and replicating the micron-sized apertures on a chip has been proposed in the past as a means of implementing the micropropulsion system. This invention describes an implementation of these micromachined FEEP thrusters where the chip with its array of thrusters is incorporated into a small module that also contains a heat sink, the metal propellant and a heater to liquefy it and maintain it in liquid form, a passive means to deliver the propellant to the thruster chip, and a communications means for controlling the thrust level and operation of the module. A typical module could be a cube 1–2 cm on a side. Many such modules can be simply bonded to the outside of a spacecraft in small or large numbers, affixed to printed wiring or powered wirelessly, to attain a truly modular FEEP propulsion system adaptable to any spacecraft shape or size.

Noncontacting transmission line junctions are useful for connecting two microwave components without introducing metal-to-metal contacts that can generate passive intermodulation products when two or more signals are present. These junctions are also useful as dc blocks that allow the transmission of microwave frequencies while preventing the transmission of direct current. At low frequencies, implementation of a broadband noncontacting junction involves a choice between large size and high-insertion loss, since the junction requires a transmission line that is one-quarter wavelength long. With this invention, the quarter wavelength section is implemented in a serpentine fashion internal to the inner conductor of the coaxial transmission line so that the physical length of transmission line required is less than one-quarter wavelength. The invention is implemented using a conductive core and a number of sleeves that fit together, with several dielectric cups interfitted between the core and sleeves. The sleeves may be stepped, notched, or otherwise shaped to precisely control the broadband frequency response. The junction provides low-frequency rejection while passing a broadband signal within a predetermined center frequency and passband. The increased functionality, low loss, and decreased volume requirement is achieved by using all of the available region inside the inner conductor of a coaxial transmission line, a region that would otherwise contain no electromagnetic fields and perform no electrical function.

Acquisition of the GPS clear/acquisition (C/A) codes in disadvantaged areas, such as buildings, is difficult because the amount of hardware needed to detect a signal and acquire the code increases as the signal-to-noise ratio decreases. This difficulty is compounded by the fact that the C/A code has data bit transitions that invert the code, randomly, at intervals of 20 milliseconds. This invention helps to improve the overall efficiency of C/A acquisition. By describing C/A as a low-density parity check (LDPC) code, it facilitates the use of existing decoding algorithms to achieve C/A acquisition by directly resolving code phase. Acquisition threshold is also improved by overcoming the issue of underlying data transitions.

Inflatable hinges for solar arrays cannot deploy to a rigid state, as mechanical hinges can. This problem can be overcome by including a curable resin with the inflatable hinge that helps rigidly position solar panels at precise angles from each other. A transparent coating is used to prevent static discharge but allows for ultraviolet light so that the resin can be cured, solidifying the hinge. Wraparound contacts can be used to connect the solar cells to flex circuits, routed to ground pads for electrical grounding.

A heptagonal antenna array (one center element surrounded by seven exterior elements) provides good rejection of both near and far sidelobes, even when the spacing between elements is increased. Compared with typical hexagonal or rectangular arrays, the heptagonal array provides better rejection of unwanted sidelobe interference for enhanced imaging quality. The heptagonal array is a low-cost alternative to larger antennas and can reduce losses due to mechanical steering. Further, the heptagonal array can have instant steering with single-beamwidth repositioning. There is no sidelobe degradation when the reflectors are electrically and mechanically steered to the same coordinate.

Interferometry provides a reliable noncontact method of analyzing microminiature components. An imaging interferometer typically comprises a laser light source to illuminate the device under test and reference mirror along with a beam splitter and microscope objectives to image the sample onto a camera. A version of this setup—the stroboscopic Michelson test system—employs a microscope objective between the beam splitter and the test sample and a second, identical microscope objective in the reference path. This invention improves upon the stroboscopic technique by moving one of the two required microscope objectives outside of the interferometer and bringing the collimated laser beam directly onto the beam splitter, test device, and reference mirror. Applications include qualification of microelectromechanical systems, which can be tested in motion under various environmental conditions. Because of the rigid construction of the device and environmental test chamber, vibration is greatly mitigated.

A typical tracking system aboard a spacecraft includes a telescope that can be controlled to keep the boresight axis pointing at a tracked star. However, stray light can interfere with tracking, causing image loss. This invention describes an optical system having front-end lenses or filters that decrease off-axis images in the periphery and preserve the fidelity of on-axis images in the center of view. Two of the invented filters have nonidentical attenuation profiles along any line extending radially from the center. A third filter’s periphery has a uniform but partial-reflective coating that is configured during manufacture in the shape of triangular wedges arranged in an equiangular fashion, providing effective gradient attenuation. Though designed to minimize noise in a star tracker, the invention can also be applied to the manufacture of common optical devices such as eyeglasses and cameras.

To improve the integrity of data in unreliable channels, the data stream can be split, compressed, and transmitted over two independent paths. However, discrete cosine transform (DCT) is not a true merge-and-split process, so when it is used for that purpose, the result is lossy data. This invention is a system for transforming and compressing data for communication or storage that can be applied to DCT type-II or DCT type-IV data. First, the DCT data is split and communicated over two channels. Then, using an inverse DCT rotator in the transform domain, the two halves are merged. The redundancy inherent in the two data blocks allows one to approximately reconstruct the original data block in case one of the two blocks is lost or corrupted during transmission. The system can also be implemented as additions to JPEG and MPEG compressors, decompressors, and communication systems for transmission over wireless communication links.

Traditionally, fluid valves operate by using a solid object to obstruct the flow path. In large integrated devices, this technique can lead to contamination, leakage, and limitations regarding operating pressure. This series of inventions relates to an electrically actuated microvalve that uses a phase-change material (such as a paraffin wax) to alternately block and unblock the flow path of a working fluid. A side channel forms a junction with the main flow channel. A heating element adjacent to the control channel and junction generates sufficient energy to melt the phase-change material, allowing it to be pumped into the junction. When the material again solidifies, it effectively holds the valve closed. Alternatively, the material can be heated to cause expansion, thereby cutting off the flow. In contrast to other phase-change valves, this device can remain in the closed position for extended periods, even when the power has been switched off.

Catalytic decomposition engines have traditionally suffered from limited thrust, low performance, and limited gas propellant options (only hydrazine). This catalytically activated transient decomposition propulsion system resolves many of these issues. It functions by injecting a pressurized monopropellant toward a catalyzing agent in a decomposition chamber, generating a gas that is then used for thrust. A solenoid valve precisely controls the flow of propellant into the chamber. Surface tension keeps the propellant in contact with the catalyst until the reaction is complete. The gas is released through an exhaust nozzle equipped with a fast-acting valve at the nozzle throat; the valve ensures that the decomposition process is given adequate time before venting. The improved density performance of the propulsion system increases the total thrust available without increasing system size, allowing greater range of usable orbits. The system is well suited for use on picosatellites and enables the use of highly energetic but stable propellants such as hydroxyl ammonium nitrate.

Dc-dc power systems often require the use of multiple power converters connected with serial input and parallel output; however, mismatches in component values can result in nonuniform distribution of converter-input voltages, which can cause power flows through individual converters to drift from uniform power distribution. The patented control scheme for uniform voltage distribution ensures uniform utilization of and uniform thermal stresses among the series-connected converters. This serial-input, parallel-output power system was designed to eliminate reliability problems associated with nonuniform converter-input voltages. It includes multiple dc-dc converters having control ports that are electrically isolated from the output voltage. Input-output isolation is achieved through a distribution voltage and differential voltages extracted from the successive floating voltages between the system input voltage and a system input ground. This system can include as many converters as desired and can further provide voltage regulation, current limiting, overvoltage protection, and undervoltage protection.

This invention describes a regulator for maximizing the power output of multiple solar array panels on small satellites. The regulator implements a peak-power-tracking algorithm to automatically provide peak power output from the solar arrays to a power bus under all conditions. The regulator includes a controller that communicates power data to a satellite processor for power management. This patent is linked to previous patents that explain a distributed power system that uses a power ring bus to connect multiple dc-dc converters, which are then connected to a solar cell mounted on a nanosatellite.

Carbon nano-onions have been observed during arc discharge and electron-beam irradiation. These processes have yielded small, circular structures ranging from 4 to 36 nanometers. It would be useful to create these carbon nanostructures in a larger size without having to employ a high-temperature process or high-energy irradiation on a substrate. This invention accomplishes that task. It uses a laser technique to deposit graphitic nano-onion structures at room temperature in an oxygenated atmosphere. The laser beam is aimed at a carbon target that faces the substrate to be coated. The resulting ablation plume impinges upon the substrate creating nested graphitic carbon structures ranging from 100 to 200 nanometers in diameter. Oxygen plays a critical role in the chemical reactions that lead to the formation of these onion structures.

Peripheral attenuating optical systems can be used in star trackers, infrared telescopes, and spacecraft related devices. This invention describes an optical system that includes a first-optical lens or filter that peripherally attenuates the signal strength of off-axis images. The on-axis images can still be seen, but without degrading the primary image. Thus, reference information from the off-axis images can be maintained. The first two of three first optical element designs can either apply a gradient or uniform filtering with no attenuation in the center. A third design can also be constructed using filters that have nonidentical attenuation profiles; in this case, the periphery has a solid reflecting coating applied during manufacture in the shape of triangular wedges equiangularly dispersed in the periphery. The wedges point toward the center of the filter, which still retains a clear transmissive portion in the middle. The concept can also be applied to the manufacture of terrestrial devices such as cameras, eyeglasses, binoculars, telescopes, and video systems.

The hypersensor-based anomaly resistant detection and identification (HARDI) system reduces the incidence of false alarms in identifying an object signature in hypersensor data. The system comprises a hypersensor, a mask and filter module, and an anomaly-suppression module. The mask and filter module iterates through the hypersensor data to generate a training mask that categorizes pixels as common background pixels or as target and anomaly pixels. The background pixels are used to generate a matched filter, and the products of that filter are used to iteratively update the training mask. The anomaly-suppression module receives and processes information pertaining to the matched filter and the categorized pixels to determine a set of mutually orthogonal matched filters for one or more targets. These filters produce a vector of filter products for different spectra that can be compared to determine whether a pixel spectrum should be rejected as an anomaly.

A combination of mechanical and electronic beam-steering techniques can be used to maintain antenna tracking when high-angular-velocity requirements exist. Two forms of antenna tracking can be used — step track and monopulse. Step tracking is an open-loop process that aligns the antenna based on the difference in power levels observed in different angular offsets. Monopulse tracking requires two types of antenna patterns from the antenna feed, one for data reception and transmission and one for antenna tracking. Variation in the antenna tracking pattern produces an error signal comprised of the ratio of the tracking and data antenna responses and a closed-loop process minimizes this error signal to align the antenna. This patent extends two previously issued patents, numbers 7,463,191 and 6,965,343.

Data transforms can be used separately or in combination to losslessly and reversibly transform, communicate, and store data in processing systems. A shared Haar transform is used on the front end, and a DCT-II, DCT-IV, or extended Haar transform is appended on the back end. The DCT-II and DCT-IV transforms are configured as a cascade connection of the front-end shared Haar transform; they produce integer outputs, so the original data can be reconstructed losslessly. The shared Haar and the appended Haar transform are cascaded to form the extended Haar transform. The shared Haar transform uses fixed angular word pairwise rotations, whereas the extended Haar transform uses adaptive angular word pairwise rotation. Using nonlinear lifting methods, the extended Haar transform becomes lossless due to the reversibility of the integer-to-integer transformation and the adaptive word pairwise rotations. The lossless block transforms, including both appended DCT and Haar wavelet transforms, are effective in preventing error propagation.

Compressed data is typically encoded with a header, which contains more important information than other data segments. Current modulation approaches treat all data segments equally—but doing so requires more bandwidth than necessary. For optimal bandwidth utilization, it would be better to maximize the reliability of the header data and permit lower reliability of the subsequent segments. This can be accomplished using unequal coding for different segments. For example, an encoder encodes one data segment while another segment is left as uncoded. The coded and uncoded data are unequally modulated with a nonuniform 16-point constellation space, which can be optimized so that a minimum amount of transmitter power is needed.